Material-feeding devices for feeding a sheet-like material in a predetermined direction have been used in printers which are employed as output devices for on-line terminal units or word processors. It is known that the material-feeding device used in the printer has a direction-correcting function for correcting the feeding direction of an inserted material to be printed, to enable a printing operation to be performed at a correct position on the material.
In printers for industrial use, such as those used for printing on a bankbook or a slip in a bank (hereinafter referred to as a bankbook printer), the printing operation may be carried out sequentially or continuously on various materials to be printed having different thicknesses. Particularly, when a notebook type material such as a bankbook is fed, the material may produce, depending on an opened page to be printed, material parts having different thicknesses, corresponding to the left and right halves relative to a stitching line of the material, so that the oblique movement of the material is liable to occur during the continuous feeding of such material parts having different thickness. Accordingly, to accommodate such a situation, it is required for the material-feeding device to possess a direction-correcting function for correctly and stably feeding various materials to be printed, having different thicknesses, to a printing area.
As a conventional material-feeding device having a direction-correcting function, the U.S. Pat. No. 4,248,151 (Real) discloses a tape guide apparatus which can be used as a printing paper guide in an impact printer. This tape guide apparatus is adapted to feed a tape in a predetermined direction while maintaining an edge of the running tape in contact with a guide reference surface, and includes a pair of rollers arranged obliquely to the reference surface but parallel to each other. The running tape is clamped or held in a nip formed between these rollers.
Also, as a conventional material-clamping device in a material-feeding device of a printer, Japanese Unexamined Patent Publication (Kokai) No. 4-22657 (JP4-22657) discloses a material-clamping device having a function for uniformly locating a front end of a material such as a bankbook or a slip. This material-clamping device is provided with a clamp section including a polygonal roller and a ball biased toward the polygonal roller and an end locating section including a retractable shutter arranged back of the clamp section in relation to the feeding direction of the material. The material is fed by the rotation of the polygonal roller and is abutted against the shutter. When being abutted on the shutter, the material is clamped or held between the ball and a circumferential corner of the polygonal roller. When the polygonal roller further rotates, the polygonal roller becomes out of contact at a circumferential flat surface portion thereof with the ball, and thereby, in this condition, the material can be conveyed toward a printing area of the printer by another conveyor roll.
It is possible that both of the above conventional material-feeding devices cannot correctly and stably feed various materials having different thicknesses. Particularly, if they are used for a thinner material, the pair of rollers or the polygonal roller/ball, acting to hold the material therebetween, may bend the material when the material is abutted against the guide reference surface or the end locating shutter to make the correct transportation of the material difficult, and also may cause creases or folds in the material.
Also, since the polygonal roller disclosed in JP4-22657 is arranged to rotate stepwise by a desired angle by means of a rotary solenoid, it is possible that the polygonal roller cannot correct the feeding direction of the material while continuously feeding the material, unlike the pair of rollers of the material-feeding device described in Real.
Accordingly, it is required to develop a material-feeding device having a direction-correcting function for correctly and stably feeding a material in a predetermined direction even though a thickness of the material might vary. Such a material-feeding device is also required in ink-jet printers which have recently become popular in various fields because of low printing noise and small body size.
As described above, in printers for industrial use, such as a bankbook printer, there is a case where, when a notebook type material is printed, the material parts having different thicknesses may be produced on the left and right sides about a stitching line of the material to be printed, depending on an opened page of the material. In this case, since it is necessary, in, e.g., a dot impact printer conventionally used generally as a bankbook printer, to maintain a distance between a printing head and a surface of the material to be printed, a level of the printing head is sequentially changed, when the material parts with difference thicknesses are subsequently printed, in response to the difference in the thickness. As a result, the conventional bankbook printer tends have a complicated driving structure for the printing head, and to require a relatively longer time from the introduction of the bankbook to its discharge after the printing.